The invention relates to a gripping unit for gripping a paper from a top surface of a stack, comprising a first and a second friction wheel having rotation axes that are mainly parallel with respect to each other and being arranged to exert a friction force on sections of a paper, the gripping unit further comprising an actuator on which the first friction wheel is mounted for moving the first friction wheel towards the second friction wheel.
Such a gripping unit for griping a paper is e.g. known in the field of computer-to-plate imaging processes, wherein printing plates are picked up from a multiple plate stack. In the stack each printing plate is sandwiched between a paper sheet to avoid damages on the surface of the plates and to avoid interaction of the printing plates surfaces, which are regularly manufactured from aluminium. In the process of handling the printing plates, elements on the stack are sequentially removed, thus in an alternating way a printing plate and a paper sheet. The printing plates are e.g. handled for processing, e.g. by exposing radiation to the printing plate. The paper sheets are removed and deposited in a box.
To remove a paper which is located on a top surface of the stack, the known gripping unit is positioned above the paper, such that the first and second friction wheels exert a friction force on sections of the paper. Then the actuator of the gripping unit moves the first friction wheel from the initial position towards the second friction wheel, so that the paper between the two friction wheels is folding upwardly and subsequently pressed between vertically oriented contact portions of the friction wheels facing each other. The paper can then be removed from the stack.
However, due to limitations which are posed by other parts of the system, it is desired that the distance between both friction wheels in the initial position is reduced, thereby also reducing the distance that the paper is moved upwards during the folding and gripping operation. As a consequence, the chance that a paper is reliably gripped by the gripping unit diminishes.